2 research outputs found
Improved procedure for the computation of Lamb's coefficients in the Physalis method for particle simulation
The Physalis method is suitable for the simulation of flows with suspended
spherical particles. It differs from standard immersed boundary methods due to
the use of a local spectral representation of the solution in the neighborhood
of each particle, which is used to bridge the gap between the particle surface
and the underlying fixed Cartesian grid. This analytic solution involves
coefficients which are determined by matching with the finite-difference
solution farther away from the particle. In the original implementation of the
method this step was executed by solving an over-determined linear system via
the singular-value decomposition. Here a more efficient method to achieve the
same end is described. The basic idea is to use scalar products of the
finite-difference solutions with spherical harmonic functions taken over a
spherical surface concentric with the particle. The new approach is tested on a
number of examples and is found to posses a comparable accuracy to the original
one, but to be significantly faster and to require less memory. An unusual test
case that we describe demonstrates the accuracy with which the method conserves
the fluid angular momentum in the case of a rotating particle